用介词填空:Koko is throwing a stone ____ a big dog.This is very silly ____ Koko.

at,of

at在这里表指向

形容词若是针对人后跟of
形容词若是针对事则后跟for

如 It's very kind of you to say so. 此处 kind是形容人
It's very important for us to learn English. 此处 important是形容“学英语”这件事

Koko is throwing a stone at a big dog.This is very silly of Koko.

at,of

to
of